U.S. patent application number 11/958867 was filed with the patent office on 2008-06-26 for activation mechanism applicable for oilfield chemicals products.
Invention is credited to Jesse Lee.
Application Number | 20080149335 11/958867 |
Document ID | / |
Family ID | 39048176 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080149335 |
Kind Code |
A1 |
Lee; Jesse |
June 26, 2008 |
Activation Mechanism Applicable for Oilfield Chemicals Products
Abstract
The invention provides a product suitable for use in an oilfield
environment comprising: a first component; a first layer
surrounding said first component, wherein said first layer is made
of a protective material able to protect the first component from
surrounding oilfield environment; a first susceptor, wherein said
first susceptor is able to interacts with a magnetic field to
generate heat.
Inventors: |
Lee; Jesse; (Paris,
FR) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION;David Cate
IP DEPT., WELL STIMULATION, 110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
39048176 |
Appl. No.: |
11/958867 |
Filed: |
December 18, 2007 |
Current U.S.
Class: |
166/285 ;
166/57 |
Current CPC
Class: |
C04B 20/12 20130101;
C09K 8/70 20130101; C04B 20/12 20130101; C04B 20/12 20130101; C04B
20/12 20130101; C04B 20/12 20130101; C04B 20/12 20130101; C09K
8/467 20130101; C04B 20/12 20130101; C04B 20/12 20130101; C04B
20/12 20130101; C09K 8/516 20130101; C04B 20/1062 20130101; C04B
2103/20 20130101; C04B 2103/20 20130101; C04B 2103/46 20130101;
C04B 2103/10 20130101; C04B 20/1066 20130101; C04B 20/1066
20130101; C04B 2103/46 20130101; C04B 20/1062 20130101; C04B
2103/408 20130101; C04B 2103/10 20130101; C04B 20/1062 20130101;
C04B 20/1062 20130101; C04B 20/1066 20130101; C04B 2103/408
20130101; C04B 20/1066 20130101 |
Class at
Publication: |
166/285 ;
166/57 |
International
Class: |
E21B 33/13 20060101
E21B033/13 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2006 |
EP |
06292018.6 |
Claims
1. A apparatus suitable for use in an oilfield environment
comprising a) a first component; b) a first layer surrounding the
first component, wherein the first layer is made of a protective
material able to protect the first component from surrounding
oilfield environment; and, c) a first susceptor, wherein the first
susceptor is able to interacts with a magnetic field to generate
heat.
2. The apparatus of claim 1, wherein the first susceptor is located
within the first layer.
3. The apparatus of claim 1, further comprising a second layer
surrounding the first component and surrounded by the first
layer.
4. The apparatus of claim 1, wherein the first susceptor is an
electrically non-conductive susceptor, and the apparatus further
comprises a second susceptor being an electrically conductive
susceptor.
5. The apparatus of claim 1, wherein the first susceptor comprises
iron oxide particles, hexagonal ferrite particles, or magnetically
soft ferrite particles.
6. The apparatus of claim 1, wherein the second susceptor comprises
elemental ferromagnetic particles or ferromagnetic alloys.
7. The apparatus of claim 1, wherein the second susceptor comprises
nickel, iron, and cobalt and combinations thereof and of their
alloys.
8. The apparatus of claim 1, wherein the first component is in
liquid state.
9. The apparatus of claim 1, wherein the first component is anyone
taken in the list accelerators, retarders, dispersants, extenders,
weighting agents, fluid-loss and lost-circulation additives.
10. The apparatus of claim 1, further comprising a second component
surrounded by the first layer along with the first component.
11. The apparatus of claim 10, wherein the first component and the
second component are further separated.
12. A method to treat a wellbore including a zone, the method
comprising: a) pumping a apparatus of claim 1 into the wellbore; b)
placing the apparatus in the vicinity of the zone; and, c) applying
an alternating magnetic field on the apparatus.
13. The method of claim 12, wherein the applying an alternating
magnetic field on the apparatus is made just before the apparatus
is placed in the vicinity of the zone.
14. The method of claim 12, wherein the step of applying an
alternating magnetic field on the apparatus is made just after the
apparatus is placed in the vicinity of the zone.
15. The method of claim 12, wherein the alternating magnetic field
is applied with a first retrievable tool lowered into the
wellbore.
16. The method of claim 12, wherein the alternating magnetic field
is applied with a second permanent tool embedded in a casing or a
tubing lowered into the wellbore.
17. The method of claim 12, further comprising ceasing the applying
an alternating magnetic field on the apparatus when the first layer
has broken.
18. The method of claim 12, wherein the alternating magnetic field
is of frequency between 2 MHz and 30 MHz.
Description
RELATED APPLICATION DATA
[0001] This application claims the benefit of EP Patent Application
06292018.6 filed Dec. 21, 2006 entitled, "NOVEL CONTROL RELEASE
MECHANISM FOR OILFIELD CHEMICAL PRODUCTS"
FIELD OF THE INVENTION
[0002] The present invention broadly relates to well cementing.
More particularly the invention relates to a composition useful to
encapsulate other composition and to release it easily. The
composition of the invention applies especially for wells from a
subterranean reservoir, such as for instance an oil and gas
reservoir or a water reservoir.
DESCRIPTION OF THE PRIOR ART
[0003] During a hydrocarbon well drilling operation and after a
hydrocarbon well has been drilled, various fluid injecting
operations are generally carried out. The fluid injecting
operations serves various purposes, for example delivering a
chemical mixture into a fluid present in the borehole for
consolidation purpose or fracturing purpose, or delivering a
chemical mixture into a cement slurry for borehole cementing
operation.
[0004] Subsequently, cementing operations are generally undertaken
to seal the annulus (i.e. the space between the well-bore and the
casing where fluid can flow). A first application is primary
cementing which purpose is to achieve hydraulic isolation around
the casing. Other applications are remedial cementing which
purposes are to stabilize the well-bore, to seal a lost circulation
zone, to set a plug in an existing well or to plug a well so that
it may be abandoned. The cement may be pumped into the well casing
through a casing shoe near the bottom of the bore-hole or a
cementing valve installed in the casing so that the cement is
positioned in the desired zone.
[0005] Cementing engineers prepare the cementing operations by
determining the volume and physical properties of cement slurry and
other fluids pumped before and after the cement slurry. In many
situations, chemical additives are mixed with the cement slurry in
order to modify the characteristics of the slurry or set cement.
Cement additives may be broadly categorized as accelerators (i.e.
for reducing the time required for the set cement to develop
sufficient compressive strength to enable further operations to be
carried out), retarders (i.e. for increasing the thickening time of
cement slurries to enable proper placement), dispersants (i.e. for
reducing the cement slurry viscosity to improve fluid-flow
characteristics), extenders (i.e. for decreasing the density or
increasing the yield of a cement slurry), weighting agents (i.e.
for increasing or lightening the slurry weight), fluid-loss or
lost-circulation additives (i.e. for controlling the loss of fluid
to the formation through filtration) and special additives designed
for specific operating conditions.
[0006] Because cement additives have an effect as soon as they are
mixed with the cement slurry, it is important that cement additives
are injected in the cement slurry at the proper time and at the
desired location in the well-bore. However, as the cement is pumped
to the bottom hole of the wellbore first before being allowed to
set and this pumping usually takes time; there is a need to find a
way to add chemicals directly in the well when needed. Various
solutions were proposed: use a downhole apparatus to directly
release the chemicals when needed, use a retardation process of the
chemicals so that it becomes active only downhole, use an
encapsulation of the chemicals and breaks this encapsulation
downhole.
[0007] The proposed invention finds a new approach to encapsulate
the chemicals. Also, it is noted that this technique does not only
apply to cementing application but to all type of chemical release
for oilfield application.
SUMMARY OF THE INVENTION
[0008] The present invention disclose a product suitable for use in
an oilfield environment comprising: a first component; a first
layer surrounding said first component, wherein said first layer is
made of a protective material able to protect the first component
from surrounding oilfield environment; a first susceptor, wherein
said first susceptor is able to interacts with a magnetic field to
generate heat.
[0009] Preferably, the first susceptor is located within the first
layer. This embodiment procures an easy way to create the
protective shell. Alternatively, the product further comprises a
second layer surrounding the first component and surrounded by said
first layer.
[0010] Preferably, the first susceptor is an electrically
non-conductive susceptor, and the product further comprises a
second susceptor being an electrically conductive susceptor. In a
first example of realization, the first susceptor comprises iron
oxide particles, hexagonal ferrite particles, or magnetically soft
ferrite particles. In a second example of realization, the second
susceptor comprises elemental ferromagnetic particles or
ferromagnetic alloys. In another example, the second susceptor
comprises nickel, iron, and cobalt and combinations thereof and of
their alloys.
[0011] Preferably, the first component is in liquid state. And/or
the first component is anyone taken in the list accelerators,
retarders, dispersants, extenders, weighting agents, fluid-loss and
lost-circulation additives.
[0012] In another embodiment, the product further comprises a
second component surrounded by the first layer along with the first
component. Preferably, the first component and the second component
are further separated through an internal wall inside the first
layer and/or inside the second layer.
[0013] In another aspect of the invention a method to treat a
wellbore including a zone is disclosed, the method comprising the
steps of: pumping a product as disclosed above into said wellbore;
placing said product in the vicinity of said zone; and applying an
alternating magnetic field on said product.
[0014] In one example, the step of applying an alternating magnetic
field on said product is made just before said product is placed in
the vicinity of said zone. In a second example, the step of
applying an alternating magnetic field on said product is made just
after said product is placed in the vicinity of said zone.
[0015] In a third example, the alternating magnetic field is
applied with a first retrievable tool lowered into the wellbore. An
in a fourth example, the alternating magnetic field is applied with
a second permanent tool embedded in a casing or a tubing lowered
into the wellbore.
[0016] Preferably, the method further comprises the step of ceasing
the step of applying an alternating magnetic field on said product
when said first layer has broken. And/or the alternating magnetic
field is of frequency between 2 MHz and 30 MHz.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Further embodiments of the present invention can be
understood with the appended drawings:
[0018] FIG. 1A shows the product according to the invention in a
first embodiment before activation.
[0019] FIG. 1B shows the product according to the invention in a
first embodiment after activation and in its broken state.
[0020] FIG. 2A shows another example of the product according to
the invention in a first embodiment before activation.
[0021] FIG. 2B shows another example of the product according to
the invention in a first embodiment after activation and in its
broken state.
[0022] FIG. 3 shows the product according to the invention in a
second embodiment.
[0023] FIG. 4 shows the product according to the invention in
another embodiment.
DETAILED DESCRIPTION
[0024] The products of the present invention are designed to
enclose and/or protect their contents until an intended site of
delivery or conditions of delivery are encountered, therefore they
can be called delivery capsules. In this way, they can be used as a
means to contain potentially hazardous or difficult-to-handle
components and to deliver such components to a well bore or a
surrounding subterranean formation to perform a desired function.
The delivery capsules of the present invention also may be used
with any downhole fluids where it is desirable to have components
separated until they are released so that they may react with each
other and/or the formation. Examples of such downhole fluids
include inter alia drilling, completion and workover fluids. FIG.
1A shows an example of the delivery capsule of the present
invention for handling a first component 10.
[0025] In most embodiments, the delivery capsules of the present
invention may be spherical, ovoid or cylindrical in shape. In a
first embodiment, the product is made of a capsule comprising only
one chamber (FIGS. 1 and 2). In a first example of this first
embodiment, the delivery capsule is made of only one protective
wall called a first layer 12 (FIG. 1A). In a second embodiment, the
capsule comprises at least two chambers (FIGS. 3 and 4) containing
a first and a second chemical component. In certain embodiments the
two chambers within the delivery capsule preferably are separated
by an impermeable dividing wall which among other things prevents
mixing of the chemical components contained in each chamber. In
preferred embodiments, the dividing wall should not allow one
chemical component in one chamber to mix with a second chemical
component in the second chamber. If desired these two chambers may
be divided into subchambers, e.g., each chamber may be divided into
at least one other subchamber (FIG. 4 showing a capsule with four
chambers). Such embodiments may be useful wherein it is desirable
to provide or facilitate the delivery of more than two chemical
components to the well bore or the subterranean formation
surrounding the well bore.
[0026] In the second embodiment, the first chemical component and
the second chemical component may be completely separated by the
dividing wall until delivery or release of the chemicals into the
subterranean formation. The first chamber and the second chamber
may be of similar size and shape or of different size and; shape,
e.g., when different proportions of the first chemical component
and the second chemical component are needed for the desired
application. Typically, the delivery capsules of the present
invention range from about 3 mm to about 20 mm in size, but other
sizes may also be suitable, depending on the chemical components to
be supplied and the purpose of using the delivery capsules. One of
ordinary skill in the art, with the benefit of these disclosures
will recognize the appropriate embodiment(s) of the capsules of the
present invention that are suitable for a chosen application.
[0027] Each chamber in a delivery capsule may contain a chemical
component to be carried downhole for a chosen application. In
certain embodiments, the chambers may contain different chemical
components that may perform different functions once released. For
instance, the capsule could contain both a cement-expanding agent
and a cement accelerator for release in a well bore cement
composition. In other embodiments, each chamber may contain a
different chemical that, when released, combines to perform a
desired function downhole.
[0028] For example, in an embodiment, the first chemical component
in the first chamber of a delivery capsule of the present invention
and the second chemical component in the second chamber of the same
delivery capsule, when released, react to form an acid downhole
that can be used, for example, to acidize a chosen portion of the
subterranean formation. For instance, in an example of this
embodiment, the first chemical component comprises a formaldehyde
solution and the second chemical component comprises an ammonium
salt. When the formaldehyde solution and the ammonium salt are
released upon the degradation of the capsule, they react with one
another to form an acid. The resultant acid may be used, inter
alia, to acidize a portion of the subterranean formation
surrounding the well bore. In another embodiment, a first chemical
component contained in a first chamber of a delivery capsule of the
present invention and a second chemical component in a second
chamber of the same delivery capsule, when released, react to form
a gas. For instance, the first chemical component may comprise
aluminum powder and the second chemical component may comprise a
liquid caustic such as sodium hydroxide. This embodiment may be
useful in applications wherein it is desirable to impart a gas to a
fluid or composition. One example is the foaming of a cement
composition to reduce its density.
[0029] The chemical components contained within the chambers of the
delivery capsules of the present invention may be liquids, solids
(e.g., powders), and/or gases, as is necessary for a chosen
application. In most embodiments, the different chambers of the
delivery capsules will contain different materials, possibly in
different forms, e.g., liquid, solid, slurry, etc.
[0030] The delivery capsules of the present invention are
preferably made from a degradable material that degrades when
subjected to downhole stimulus (or activation) so as to release the
chemical components that are contained in the chamber(s) of the
delivery capsules into the well bore. For this reason, the
degradable material contains at least one susceptor 11 (FIGS. 1 to
4) and preferably several susceptors. So, the present invention
uses the combination of an induction heating means and susceptors
for triggering the break of the degradable material (FIGS. 1B and
2B).
[0031] Therefore, according to the invention a combination of at
least one susceptor and high frequency alternating magnetic fields
is used, susceptor generating heat thanks to the alternating
magnetic fields so that heat be sufficient to begin a modification
of the shell of the product (i.e. the capsule made of the
degradable material). The modification can be the degradation or
decomposition in itself, a transformation of composition or state
(melting) of the delivery capsule, a weakening of the delivery
capsule creating a further break, or a break of the delivery
capsule. Both ferromagnetism in a ferromagnetic material and
ferrimagnetism in a non-conductive ferromagnetic material
disappears at the Curie temperature as thermal oscillations
overcome the orientation due to exchange interaction, resulting in
a random grouping of the atomic particles. When a non-conductive
ferrimagnetic material is placed in an electromagnetic field, the
hysteresis losses in the material cause its temperature to rise,
eventually reaching its Curie temperature. Upon reaching its Curie
temperature, the material crystal lattice undergoes a dimensional
change, causing a reversible loss of magnetic dipoles. Once the
magnetic dipoles are lost, the ferrimagnetic properties cease, thus
halting further heating.
[0032] The delivery capsule made of the first layer coating is made
of any type of protective material able to protect the chemical
component(s) of the capsule from the surrounding downhole
fluids.
[0033] Preferably, the invention involves the use of at least two
different susceptors (11 and 13 in FIGS. 1 to 4) within the
delivery capsule that heat, under an alternating magnetic field.
Thanks to this combination of two susceptors, they heat at an
unexpectedly quick rate. More specifically, the invention provides
heating agents that heat at average heating rates greater than
300.degree. C./s (575.degree. F./s) to activate initiator that will
initiate a polymerization chain reaction such that a solid/gel
polymer is created. Patent application WO03063548 uses a
combination of a first non-conductive susceptor and a second
electrically conductive susceptor, benefits of this combination
seems to be the rapid heating phenomenon. Also, the addition of the
second susceptor type helps to focus the magnetic field on the
non-conductive susceptors, enabling the temperature to continue to
rise rapidly. As described in the patent application WO03063548,
among the important parameters in the process of using two types of
susceptors are the following: size and shape of the ferrimagnetic
hysteresis loop, susceptor loading, alternate heating mechanisms,
particle shape. The term "susceptor" as used herein refers to a
material that interacts with a magnetic field to generate a
response, e.g., eddy currents and/or hysteretic losses. The method
and apparatus of the present invention are based on the use of dual
"susceptors" in oilfield applications that can be used to heat
monomers and associated initiator such that a polymerization chain
reaction begins and said monomers create a polymer able to form a
solid/gel mass. The susceptors are further described below.
[0034] Preferably, in the product, the susceptors comprise (a) at
least one plurality of electrically non-conductive susceptors and
(b) at least one plurality of electrically conductive susceptors.
The method and product of the present invention utilize the fact
that magnetic induction heating occurs in magnetic or electrically
conductive materials when they are subject to an applied
alternating magnetic field. The present invention takes advantage
of the heating that occurs in the combination of susceptors
described herein. When a current-carrying body, or coil, is placed
near the susceptors of the present invention, the magnetic field
caused by the current in the coil induces a current in the
susceptors. In the electrically conductive magnetic susceptors,
heating occurs by both eddy current and hysteresis losses. It is
eddy currents losses that dominate. In the non-conducting magnetic
materials, heating occurs by hysteresis losses. In this later case,
the amount of energy available for heating is proportional to the
area of flux vs. field intensity hysteresis curve (B vs. H) and
frequency of the alternating field. This mechanism exists as long
as the temperature is kept below the Curie point (T.sub.c) of the
material. At the Curie point, the originally magnetic material
becomes non-ferromagnetic. Thus, at its T.sub.c heating of the
magnetic material ceases. The combination of these conductive and
non-conductive susceptors as described herein produces a rapid rate
of heating, e.g., greater than 300.degree. C./s.
[0035] The electrically non-conductive susceptors are preferably
micron-sized ferrimagnetic particles. Examples of the electrically
non-conductive particles include, but are not limited to, iron
oxides, hexagonal ferrites, or magnetically soft ferrites. Examples
of hexagonal ferrites include compounds that have the composition
SrF, Me.sub.a-2W, Me.sub.a-2Y, and Me.sub.a-2Z, wherein 2W is
BaO:2Me.sub.3O:8Fe.sub.2O.sub.3, 2Y is
2(BaO:Me.sub.3O:3Fe.sub.2O.sub.3), and 2Z is
3BaO:2Me.sub.3O:12Fe.sub.2O.sub.3, and wherein Me.sub.a is a
divalent cation. Examples of the magnetically soft ferrite
particles have the composition 1MebO:1Fe.sub.2O.sub.3, where
Me.sub.bO is a transition metal oxide. Me.sub.a comprises Mg, Co,
Mn or Zn and Me.sub.b comprises Ni, Co, Mn, or Zn. In preferred
embodiments the electrically non-conductive particles, e.g.,
ferrimagnetic particles, have a size of from about 1 .mu.m to about
50 .mu.m. The electrically non conductive particles comprises from
about 20.sup.w/o (10.sup.v/o) to about 58.sup.w/o (30.sup.v/o) of
the composition. Examples of useful hexagonal ferrites include
those shown in Table 1:
TABLE-US-00001 TABLE 1 Me-2W Me-2Y Me-2Z
Co.sub.2Ba.sub.1Fe.sub.16O.sub.26 Co.sub.2Ba.sub.2Fe.sub.12O.sub.22
Co.sub.2Ba.sub.3Fe.sub.24O.sub.41
Co.sub.1Zn.sub.1Ba.sub.1Fe.sub.16O.sub.26
Co.sub.1Zn.sub.1Ba.sub.2Fe.sub.12O.sub.22
Co.sub.1Zn.sub.1Ba.sub.3Fe.sub.24O.sub.41
Mg.sub.2Ba.sub.1Fe.sub.16O.sub.26 Mg.sub.2Ba.sub.2Fe.sub.12O.sub.22
Mg.sub.2Ba.sub.3Fe.sub.24O.sub.41 Mg.sub.1Zn.sub.1Ba1Fe16O26
Mg.sub.1Zn.sub.1Ba.sub.2Fe.sub.12O.sub.22
Mg.sub.1Zn.sub.1Ba.sub.3Fe.sub.24O.sub.41
Mn.sub.2Ba.sub.1Fe.sub.16O.sub.26 Mn.sub.2Ba.sub.2Fe.sub.12O.sub.22
Mn.sub.2Ba.sub.3Fe.sub.24O.sub.41
Mn.sub.1Zn.sub.1Ba.sub.1Fe.sub.16O.sub.26
Mn.sub.1Zn.sub.1Ba.sub.2Fe.sub.12O.sub.22
Mn.sub.1Zn.sub.1Ba.sub.3Fe.sub.24O.sub.41
[0036] See L. L. Hench and J. K. West: "Principles of Electronic
Ceramics" (John Wiley & Sons 1990) pp. 321-325. The
ferromagnetic hexagonal ferrites are also known as hexagonal
ferrimagnetic oxides. Examples of preferred ferrimagnetic hexagonal
ferrites include SrF, Co-2Y and Mg-2Y. A range of Curie
temperatures is preferred for the susceptors to be effective in
activating different types of initiators.
[0037] Other non-conducting particles comprise magnetically soft
ferrite particles having the structure 1MeO:1Fe.sub.2O.sub.3, where
MeO is a transition metal oxide. Examples of Me include Ni, Co, Mn,
and Zn. Preferred particles include: (Mn,ZnO)Fe.sub.2O.sub.3 and
(Ni,ZnO)Fe.sub.2O.sub.3, also referred to as MnZn and NiZn
ferrites, respectively. Even though "soft" ferrites have a narrower
hysteresis loop than the "hard" ferrites, efficient heating with
"soft" ferrites is achievable under proper processing conditions,
e.g., power level and frequency, that utilize the total hysteresis
loop area.
[0038] The electrically conductive susceptors are preferably
ferromagnetic particles and intrinsically conductive polymer (ICP)
particles. The electrically conductive ferromagnetic particles can
be elemental ferromagnetic particles or ferromagnetic alloys.
Examples of electrically conductive particles comprise; nickel iron
and cobalt and combinations thereof and of their alloys. Preferred;
ferromagnetic particles have a size of from about 5 .mu.m to about
100 .mu.m, more preferably from about 10 .mu.m to about 50 .mu.m.
Intrinsically conductive polymers (ICPs) are organic polymers that
conduct electric currents while retaining the other typical
properties commonly associated with a conventional polymer. ICPs
are different from so-called conducting polymers that are merely a
physical mixture of a non-conducting polymer with a conducting
material such as metal or carbon powder. In addition to the
generation of heat by hysteresis losses in the ferrimagnetic
particles eddy current losses within the electrically conductive
polymer contribute additional heating to enhance the rate of
heating of the heating agent. Since ICPs tend to lose their
electrical conductivity at temperatures above about 200.degree. C.
heating agents utilizing ICPs are preferably used in applications
in which the maximum process welding temperature is below
200.degree. C. Examples of ICPs include polyaniline, polypyrrole,
polythiophene, polyethylenedioxythiophene, and poly (p-phenylene
vinylene). The electrically conductive particles preferably have a
size of from about 5 .mu.m to about 100 .mu.m, more preferably,
from about 10 .mu.m to about 50 .mu.m and comprise from about
10.sup.w/o (5.sup.v/o) to about 29.sup.w/o (15.sup.v/o) of the
composition.
[0039] Examples of dual susceptor formulations include Strontium
Ferrite/Flake Nickel; Mn--Zn Ferrite/Flake 97Ni-3Al; Mn--Zn
Ferrite/Iron.
[0040] The product and method of the present invention enable the
use of standard coil constructions and the use of available
induction generators. The coil current used in the present
invention ranges from about 50 to about 150 A. The method of the
present invention produces rapid heating rates at lower coil
currents. According to the type of susceptors used, the frequency
and the strength of the magnetic field are adjusted so it can be
used to induce heating for activation of the initiator. Preferably
the useful frequency range is from about 2 MHz to about 30 MHz and
the preferred power ranges from about 1 kW to about 7.5 kW. Where
the desired temperature is higher the frequency and power will be
at the higher end of the range, e.g., from about 10 MHz to about 15
MHz.
[0041] Depending on the susceptors used, the field generated by the
induction coil influences the heating patterns of the susceptors
and the field is a function of the coil geometry. Examples of coil
design include solenoid, pancake, conical and Helmholtz. While
these coil types are among those commonly used by industry, certain
embodiments of invention may require specialized coils. For
example, in certain embodiments solenoid coils are preferred
because solenoid coil geometry produces a very strong magnetic
field. In other embodiments, pancake coils are used. Pancake coils
have been found to produce a non-uniform field with its maximum at
the center. Magnetic field strength increases with increasing
number of coil turns, increasing coil current and decreasing
coil-work piece separation. The factors can be readily manipulated
by one of ordinary skill in the art to select combinations of these
factors to obtain the desired magnetic field strength. Solenoid
coil geometry produces the strongest field of all the possible
geometries. Pancake coils are most common in one-sided heating
applications. Changing the coil parameters (e.g., spacing between
turns or the number of turns) can change the field values, but the
pattern is generally the same.
[0042] One also needs to take the coil design (for induction
heating) into consideration depending on the various types of
methods of use. So, a solenoid coil can be used to trigger the
release of material flow through it and a pancake coil design can
be used to trigger the release of chemicals above or in front of
it.
[0043] In a second example of the first embodiment of the product,
the delivery capsule is made of two protective walls called a first
layer 12 and a second layer 14 (FIG. 2A). The second layer
surrounds the first component and is surrounded by the first layer.
The first layer is of the type described above, whereas the second
layer is either also of the type described above or of the type
degradable material as described below. Aim of this combination of
two different types of coating ensure a controlled release of the
chemical components in two steps: a first step by activating the
susceptor through the method described above to break the first
layer for releasing delivery capsule with second layer and a second
step allowing the second layer to be degraded for finally releasing
the chemical component(s). This combination is quite useful when
double release is needed.
[0044] The second layer may preferably include degradable materials
as degradable polymers. Such degradable materials may be capable of
undergoing an irreversible degradation downhole. The term
"irreversible" as used herein means that the degradable material,
once degraded downhole, should not recrystallize or reconsolidate
while downhole, e.g., the degradable material should degrade in
situ but should not recrystallize or reconsolidate in situ. The
terms "degradation" or "degradable" refer to both the two
relatively extreme cases of hydrolytic degradation that the
degradable material may undergo, i.e., heterogeneous (or bulk
erosion) and homogeneous (or surface erosion), and any stage of
degradation in between these two. This degradation can be a result,
inter alia, of a chemical or thermal reaction or a reaction induced
by radiation. We should be mindful that the degradability of a
polymer depends at least in part on its backbone structure. For
instance, the presence of hydrolyzable and/or oxidizable linkages
in the backbone often yields a material that will degrade as
described herein. The physical properties of degradable polymers
depend on several factors such as the composition of the repeat
units, flexibility of the chain, presence of polar groups,
molecular mass, degree of branching, crystallinity, orientation,
etc. For example, short-chain branches reduce the degree of
crystallinity of polymers while long-chain branches lower the melt
viscosity and impart, inter alia, elongational viscosity with
tension-stiffening behavior. The properties of the material
utilized can be further tailored by blending, and copolymerizing it
with another polymer, or by a change in the macromolecular
architecture (e.g. hyper-branched polymers, star-shaped, or
dendrimers, etc.). The properties of any such suitable degradable
polymers (e.g., hydrophobicity, hydrophilicity, rate of
degradation, etc.) can be tailored by introducing select functional
groups along the polymer chains. For example, poly(phenyllactide)
will degrade at about With of the rate of racemic poly(lactide) at
a pH of 7.4 at 55.degree. C.
[0045] Suitable examples of degradable materials that may be used
in accordance with the present invention include, but are not
limited to, those described in the publication of Avarices in
Polymer Science, Vol. 157, entitled "Degradable Aliphatic
Polyesters" and edited by A. C. Albertsson, pages 1-138. Examples
include homopolymers, random, block, graft, and star-and
hyper-branched aliphatic polyesters. Polycondensation reactions,
ring-opening polymerizations, free radical polymerizations, anionic
polymerizations, carbocationic polymerizations, coordinative
ring-opening polymerizations, and any other suitable process may
prepare such suitable polymers. Specific examples of suitable
degradable materials include polysaccharides such as dextrans or
celluloses; chitins, chitosans; liquid esters (e.g., triethyl
citrate); proteins (e.g. gelatin); aliphatic polyesters;
poly(lactides); poly(glycolides); poly(s-caprolactones);
poly(hydroxybutyrates); poly(anhydrides); aliphatic
poly(carbonates); ortho esters, poly(orthoesters); poly(amino
acids); poly(ethylene oxides); and poly(phosphazenes). Other
suitable materials include heat-sealable materials, other
thermoplastic materials, or those that may be dissolved with an
appropriate solvent. Examples include hydroxy propyl
methylcellulose, pectin, polyethylene oxide, polyvinyl alcohol,
alginate, polycaprolactone, gelatinised starch-based materials, and
the like. In one embodiment, hydroxy propyl methylcellulose MC) is
used.
[0046] In alternative embodiments, the delivery capsules may be
coated with coatings that, inter alla, may facilitate the
dispersion of the delivery capsules in a fluid or composition or,
in some way, alter the solubility of the delivery capsules in the
subterranean environment. Suitable coatings, include, but are not
limited to, gum arabics, pectins, and alginates. Such coatings may
be used to impart a degree of resistance, if desired, to the
delivery capsule's solubility. For instance, gum arable, pectin,
and alginate all have a slight retarding effect on HPMC solubility;
the extent of the effect may vary, depending on the thickness of
the coating. This may be desirable when a delay period is
beneficial before the chemical components contained within the
delivery capsules are released. Also, both pectin and alginate may
be cross-linked to provide a degree of pH resistance to the
delivery capsules so that they will not degrade so as to release
their contained chemical components until a desired pH is
encountered.
[0047] In choosing the appropriate degradable material, one should
consider the degradation products that will result. These
degradation products should not adversely affect other operations
or components The choice of degradable material also can depend, at
least in part, on the conditions of the well, e.g. wellbore
temperature. For instance, lactides have been found to be suitable
for lower temperature wells, including those within the range of
15.degree. C. to 65.degree. C., and polylactides have been found to
be suitable for well bore temperatures above this range. Also,
poly(lactic acid) may be suitable for higher temperature wells.
Some stereoisomers of poly(lactide) or mixtures of such
stereoisomers may be suitable for even higher temperature
applications Also, in some embodiments, it is desirable for the
degradable material to degrade slowly over time as opposed to
instantaneously.
[0048] In alternative embodiments, different degradable materials
(in terms of thickness and/or composition and/or coatings) may be
used to define the different chambers in a capsule of different
capsules within a composition. For instance, using a thicker
material to define one chamber in a capsule may result in a
slightly delayed release of the chemical component within that
chamber. In this way, it is possible to provide for the release of
different chemical components in the chambers under different
conditions, for instance, different temperatures or at different
pHs. In one embodiment, such different degradable materials in a
capsule may be used to facilitate the delivery of a first chemical
component to one portion of the well bore and the delivery of a
second chemical component to a second portion of the well bore.
[0049] If the application in which the degradable delivery capsule
will be used does not contain a component that will enable the
degradable material to degrade, e.g., in a dry gas hole, then in
alternative embodiments of the present invention, the degradable
material can be mixed with inorganic or organic compound. In
preferred alternative embodiments, the inorganic or organic
compound is hydrated. Examples of the hydrated organic or inorganic
solid compounds that can be utilized, include, but are not limited
to, hydrates of organic acids I or their salts such as sodium
acetate trihydrate, L-tartaric acid disodium salt dihydrate, sodium
citrate dihydrate, hydrates of inorganic acids, or their salts such
as sodium tetraborate decahydrate, sodium hydrogen phosphate
heptahydrate, sodium phosphate dodecahydrate, amylose, starch-based
hydrophilic polymers, and cellulose-based hydrophilic polymers. Of
these, sodium acetate trihydrate is preferred. The lactide units of
the aliphatic polyester and the releasable water of the organic or
inorganic solid compound utilized are preferably present in the
mixture in equal molar amounts. The degradable material is then in
a sense self-degradable, in that the degradable should at least
partially degrade in the releasable water provided by the hydrated
organic or inorganic compound, which dehydrates over time when
heated in the subterranean zone.
[0050] According to the invention, products described herewith can
be used in various methods in oilfield applications. Examples are:
in primary cementing technique, the product can be used to release
cement accelerator at the bottom of the casing to significantly
reduce the wait on cement time and to minimize setting in the pipe;
in curing loss circulation and spotting fluid loss pills, the
product can be used to release the crosslinker on demand so to
obtain the solid/gel right before the fluid entering the loss zone;
in hydraulic fracturing, the product can be used to deliver
crosslinker immediately before the fluid entering the fracture and
to minimize the negative impact of tortuosity on crosslinked
fluids; and alternatively, the product can be used to improve the
success rates for spotting cement plugs by controlling the cement
setting time precisely.
* * * * *